When it comes to climate warming, cow burps are no joke

The dairy cows in an outdoor feedlot at the University of Minnesota in Morris eat a mix of hay, corn silage and grain.

But every day they also get an ounce of a seaweed harvested in Hawaii.

“This red seaweed has been shown to reduce methane by at least 40 percent, and maybe more,” said professor Brad Heins.

Heins knows that because he uses a device mounted on a small trailer to measure the methane when the cows burp.

The cows are trained to come to this device for some “cow candy” — small pellets of tasty corn. The computer reads a tag on the cow’s ear and dispenses the treats long enough to keep the cow’s nose in the sniffer for at least three minutes.  

“You’re going to get maybe three to four good burps out of a cow during that time period, and that's when the methane will peak quite high,” explained Heins.

The goal is to measure methane output from each cow seven to 10 times a day.

“I limit the cows. If they come in and get a collection, they can’t come in for another two hours. Otherwise, you’d get boss cows in there just eating pellets all day and you’re not getting methane measurements on other cows,” said Heins.

Methane is a by-product of fermentation as cows digest their food. Methane is also released from liquid manure stored on farms, but cow burps are the largest source.

Production of methane changes based on a cow’s size, what they eat and even, according to research by Heins, by the time of day.

Methane is found at much lower levels than the primary greenhouse gas carbon dioxide, but it has a much greater impact on climate warming. Methane also cycles through the atmosphere much more quickly than carbon dioxide.

Experts believe making reductions now in methane could slow global warming and buy time for longer-term strategies to limit carbon dioxide emissions.

Seaweed is not the only feed additive being tested to adjust a cow’s gut microbiome to produce less methane.

Researchers are also looking to genetics. U of M researchers are beginning an investigation of methane production from cows in a special herd maintained in St. Paul.

“We have a small herd of 1964 genetic Holsteins in St. Paul, so they are basically frozen in time and their genetics are from the 1960s,” said Heins. “We can maybe see if there are genes regulating methane that are different in the 1960s versus today.

But it's not clear when these potential solutions will be available outside of the research lab in barns and pastures. 

“If it were simple and we could just feed a feed additive that would eliminate methane production, we would have done it 25 years ago,” said U of M assistant professor Isaac Salfer, who specializes in cow nutrition.

Salfer said unanswered questions include the cost of methane-reducing feed additives. Dairy farms operate on thin profit margins he said, and farmers are likely to reject costly additives. 

And the microbes in a cow’s gut are not static, but rapidly evolving.  

“So, when you feed these compounds, they reduce in efficacy over time. They might reduce methane production for one month. But after they're fed for a month, the microbial population adapt.”  

That would require farmers to regularly monitor methane from their cows, so they could switch feed additives if one becomes ineffective.

Salfer and Heins believe this work will lead to methane reduction, they just can’t say when that will happen. Heins said additives are not being used on farms now, and it will require a huge effort to scale up production of a product such as red seaweed to feed millions of cows across the country.

“We know that there's a lot of targeted methane reductions that everybody wants to meet by 2030 or 2050. But a lot of this is in the early stages, especially from a feed supplement standpoint,” said Heins. “We probably need to ramp up our research a lot faster to be able to get to those dates and reduction targets."

While Heins and other researchers look to feed additives and animal genetics to slow methane production in cows, Ben Lilliston worries the problem is getting worse.

“Our methane emissions are actually rising when it comes to agriculture both in Minnesota and around the country,” he said.

Lilliston is director of climate and rural strategies at the Minneapolis-based Institute for Agriculture and Trade Policy. He blames rising methane emissions on the shift from smaller to larger animal operations 

“So even if you are able to reduce methane emissions by a marginal amount through the feed, if you continue to add animals to that system then that’s going to increase your absolute emissions,” Lilliston said.

Lilliston said methane emissions can be reduced by changing how large farms handle manure, and he thinks feed additives like seaweed hold promise in the future.

However, he’s convinced the only way to quickly limit methane is to reduce the number of cows, while acknowledging that’s a solution most Americans are unlikely to embrace.

“Can we start to think about how much milk we actually need to produce? And how much beef do we actually need to produce? We need to start having some of these tough conversations,” Lilliston said. 

“Can we just do some tweaks to the current system of agriculture, and will that be enough, or do there need to be more serious and drastic steps taken?”